Fig. 4: CD9 expression is increased in transitional cluster 9 and regulates JQ1 resistance in SUM149.

A Likelihood of cells remaining in the SCLED cluster based on CD9 expression. B CD9 levels of individual cells are mapped on the graph in Fig. 1A. C Scatter plot shows Pearson correlation of average CD9 expression and cluster 9 signature in each dataset in Fig. 3. D Violin plot shows indicated motif activity of CD9 high cluster and CD9 low cluster in K562 and MDAMB468 cells. E Kaplan–Meier curve of relapse-free survival in patients with basal-like breast cancer (n = 65 or n = 165) based on low or high CD9 protein split on median level. Significance is determined by log-rank test. F Changes of in vitro stemness score of SUM149 transfected with shCON or shCD9-1 lentivirus treated with JQ1 (100 nM) for 96 h, 8 days and 10 days. In vitro stemness markers included SETD6, NANOG, POU5F1, MALAT1, and NEAT1 were assessed by RT-PCR and in vitro stemness score calculated as un weighted sum of relative fold change of each gene compared to shCON cells treated with DMSO and shCD9 cells treated with DMSO, respectively. Data represent SEM of three replicates. G Changes of in vitro stemness score of SUM149 treated with JQ1 (100 nM), anti-CD9 and combination for 96 h, 8 days and 10 days. H Cell viability assessed by prestoblue of SUM149 transfected with shCON, shCD9-1, shCD9-2, and shCD9-3 lentivirus and treated with indicated doses of JQ1 for 96 h. I Scatter plot of correlation of cell growth assessed by prestoblue and CD9 expression (left). Scatter plot of cell sensitivity to JQ1 and CD9 expression (right).